change: Use optimized reference hash sets for entity tracking

These avoid allocations of iterators and are a bit faster for most operations

src/main/java/me/jellysquid/mods/lithium/common/entity/tracker/EntityTrackerEngine.java

@@ -1,14 +1,18 @@
 package me.jellysquid.mods.lithium.common.entity.tracker;
 
 import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
 import me.jellysquid.mods.lithium.common.entity.tracker.nearby.NearbyEntityListener;
 import me.jellysquid.mods.lithium.common.entity.tracker.nearby.NearbyEntityListenerProvider;
 import net.minecraft.entity.LivingEntity;
 import net.minecraft.util.math.BlockBox;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.ChunkSectionPos;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Set;
 
 /**
  * Tracks the entities within a world and provides notifications to listeners when a tracked entity enters or leaves a
@@ -169,8 +173,8 @@ private static long encode(int x, int y, int z) {
     }
 
     private class TrackedEntityList {
-        private final Set<LivingEntity> entities = new HashSet<>();
-        private final Set<NearbyEntityListener> listeners = new HashSet<>();
+        private final Set<LivingEntity> entities = new ReferenceOpenHashSet<>();
+        private final Set<NearbyEntityListener> listeners = new ReferenceOpenHashSet<>();
 
         private final long key;
 

src/main/java/me/jellysquid/mods/lithium/common/entity/tracker/nearby/NearbyEntityTracker.java

@@ -1,12 +1,12 @@
 package me.jellysquid.mods.lithium.common.entity.tracker.nearby;
 
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
 import me.jellysquid.mods.lithium.common.util.LithiumMath;
 import net.minecraft.entity.LivingEntity;
 import net.minecraft.entity.ai.TargetPredicate;
 import net.minecraft.util.math.Box;
 import net.minecraft.util.math.MathHelper;
 
-import java.util.HashSet;
 import java.util.Set;
 
 /**
@@ -20,7 +20,7 @@ public class NearbyEntityTracker<T extends LivingEntity> implements NearbyEntity
     private final int rangeC;
     private final float rangeSq;
 
-    private final Set<T> nearby = new HashSet<>();
+    private final Set<T> nearby = new ReferenceOpenHashSet<>();
 
     public NearbyEntityTracker(Class<T> clazz, LivingEntity self, float range) {
         this.clazz = clazz;